Form's Thank You Page

I am using a slightly modified version of kirupa’s php form mailer as shown below:


<?php  #formhandler.php
if(isset($_POST['btnsubmit'])) { 
$to = "me@mail.com"; 
$subject = "Form Submission"; 
$name_field = stripslashes($_POST['fullname']); 
$email_field = $_POST['email']; 
$message = stripslashes($_POST['message']); 
  
$body = "From: $name_field
 E-Mail: $email_field
 Message:
 $message"; 
  
mail($to, $subject, $body, 'From: me@mail.com');

header ('Location: http://www.mysite.com/thankyou.php'); 
} else { 
echo "Error: No data has been sent";
} 
?>

As you can see, the user is sent to thankyou.php upon successful submission of the form. What I want to know is how do I customize a message in thankyou.php to read as follows by using info from formhandler.php above:

Thank you (person’s name)…

I’ve tried a few things but I got errors. Any ideas?